In offshore drilling systems, a riser extends from the blowout preventers (BOPs) at the ocean floor to the drilling vessel floating on the ocean surface. In the presence of high current conditions, riser retrieval may not be possible. When there is a storm, such as a hurricane, that approaches the drilling site, the vessel motions in the waves are excessive and it is necessary for the drilling vessel to disconnect from the well and retrieve the riser on board. Failing to retrieve the riser, the riser joints may be damaged or the entire string dropped to sea causing significant vessel down time and financial loss to replace the lost equipment. Conventionally, the riser is disconnected at the ocean floor, and the entire riser must be retrieved and laid down in joints on the floating vessel. It is not uncommon in locations such as the Gulf of Mexico for a drilling ship to have to disconnect several times because of approaching storms during a typical hurricane season. A problem associated with the retrieval of a riser from the water in high currents is that after the riser disconnect from the sea bed, the riser experiences a relatively large top angle under the action of current load on the riser. This angle causes the riser joints to jam in the diverter housing. Pulling the riser while it is leaning on the diverter will damage the joints and the buoyancy modules. Thus, retrieval of the riser may not be possible by the conventional approach.
It would be advantageous to provide a method that would allow for retrieval of the drilling riser in high currents and extreme weather conditions without substantial modifications to the drill floor and vessel equipment.